A project that’s been going on at W88 for the past four or five months went public yesterday. We’ve been designing, prototyping and programming a PC board to be used as a conference badge at Thotcon 0x4, Chicago’s hacking conference. Yesterday around seven hundred badges were passed out to conference attendees, each badge having an Atmel processor, LED array, and 2.4 GHz transceiver. The badges were able to process location checkins from beacons throughout the room, display messages from the organizers, and report their own id to the network. Since the board includes the Atmel ATMega128RFA1 processor and an Arduino compatible form factor, the badges can be reused for many Arduino projects.
This was a big project for us, requiring a lot of late nights and a lot of learning. For the team, It’s the first W88 production board, the first experience with 2.4GHz networking, first double sided prototype, first time using a QFN processor package (with luck, also the last), first reflow rework experience – though we thought it could be done, there were many challenges. Not only did we get it done on time within planned cost, we had a lot of fun doing it.
Workshop88 has been the recipient of lots of donated electronic parts. An effort of an hour a week or so over the last several months to sort through them is starting to show some results, so some random jottings on what’s back in the lab seem useful.
An awful lot of resistors are back there. If anyone needs virtually any value of 1/8th watt thru hole resistor you can probably find it, along with a pretty full set of surface mount resistors. There are also some larger wattage resistors, though they’re not as sorted out.
The thru hole or breadboard LED supply is also well stocked. Many colors and several sizes are back there.
One useful looking find last night was a half dozen PIC processors, PIC16C745. These have built in low speed USB, so they could be used in any project that needs a USB port to control or monitor something else. While not the latest part, at least they’re from this millennium.
This is just the tip of the iceberg on what’s available in the electronics bins for members. While most of what’s there is far from leading edge, for breadboarding purposes it’s ideal. One project that Jim and I have discussed is to have a simple PCB manufacture setup right in the room, so that an idea could go from concept to populated board in a couple of hours.
The Quest Academy in Palatine is opening an “Innovation Center” next year that will include a 3D printer for the kids to use. Vinnie Vrotny, director of academic technology, asked Workshop88 to bring a couple 3D printers to a benefit event last evening. Proceeds of the event will help fund the center.
I brought the MakerBot Cupcake up to Hoffman Estates. I’d pictured a junior high gym as a venue – in fact the benefit was at a pretty upscale banquet hall. Initially I thought that jeans and hiking boots might not be suitable among the tuxedos and gowns, but I think our demo was very successful. Lots of people stopped for lengthy conversations, and were quite interested in the tech. It didn’t hurt that the printers were right next to the open bar.
We should keep some open contacts with the school, as some of our aims match well with theirs.
Last Thursday I read on Dangerous Prototypes forum about doing making PCBs by printing on vinyl and heat transferring to PC board, then etching. Vinyl was reported to transfer 100% of the toner easily, better than the sheets designed for the purpose. Since I was in need of a board, Andrew had recently gotten some vinyl at the space, and there’s a laminating machine there, it seemed worth a try.
The process is simple: laser print the circuit on some vinyl sheet that’s glued to a piece of paper, then run both the printed piece and a blank board through the laminator to transfer the toner to the copper. Paul Reich just finished a circuit board design that looked pretty challenging to etch, so that seemed a good test.
Initially I worried that putting the vinyl through the laser printer might be a little risky. Running a few small patches through didn’t show any obvious issues. The vinyl for the vinyl cutter isn’t ideal: it could be a little thinner and it’s nearly opaque so it’s hard to see whether the image is on the board.
The first quick test was quite encouraging.
Although far from perfect, in the areas that transferred the detail was quite good. Since the board hadn’t been cleaned and the board was only run through the laminator once, results were better than expected.
Saturday back at the space, I thought to try some other materials instead of borrowing the supplies for the vinyl cutter, and try some ways of cleaning the copper. Browsing the hardware turned up some Con-Tact low-tack shelf paper that seemed to be vinyl, as well as steel wool and polishing compound to clean the copper.
The shelf paper didn’t work out, as it didn’t stick to paper enough to go through the printer. Steel wool and polishing compound both appeared to clean the copper pretty well.
After some further experiments, Paul and were able to make a couple of double sided boards that were good enough to use for some of the tests we were hoping for.